Ulcerative colitis: where the inflammation is and how we control it

What part of the bowel is affected?

UC usually starts in the rectum, the final section of the large bowel, and extends upwards in a continuous area. It may involve the rectum alone (proctitis), the left side of the colon, or more of the colon. These are descriptions of extent, not inevitable stages that everyone passes through.

The inflammation mainly affects the bowel's inner lining. The pattern can look different after treatment, and severe disease can cause deeper injury. I interpret the camera findings and biopsies together rather than diagnosing UC from one picture. Crohn's disease has a different pattern, although the distinction is sometimes uncertain initially.

Symptoms can include more than diarrhoea

Common symptoms include blood or mucus in poo, urgency, loose stools, abdominal cramps and needing the toilet at night. Rectal inflammation can cause a persistent urge to go even when little comes out. Some people have constipation as well. Bleeding and inflammation can contribute to anaemia and tiredness.

IBD can also affect joints, skin, eyes or the liver and bile ducts. Tell me about symptoms outside the bowel. A painful red eye or a change in vision needs urgent assessment. UC is different from irritable bowel syndrome (IBS), although IBS-type symptoms can coexist.

How the diagnosis is confirmed

Blood tests assess inflammation, anaemia and general health. Stool tests help check for infection, which can resemble or accompany a flare. Calprotectin measures bowel inflammation but does not diagnose UC by itself. FIT measures blood and cannot confirm or exclude UC.

Colonoscopy with biopsies usually establishes the pattern and extent. If inflammation is severe, a shorter examination of the lower bowel may be more appropriate initially.

Biopsies are examined under a microscope, including samples from areas that look normal. Sometimes the first assessment is labelled IBD unclassified until further information clarifies the diagnosis.

Treating a flare and preventing another one

Mesalazine, a 5-ASA medicine, is often useful for mild or moderate UC. It may be taken by mouth, into the rectum as a suppository or enema, or by both routes. Rectal preparations reach the lower bowel directly. Tell us if using them is difficult so the preparation or plan can be reviewed.

Steroids may help bring a flare under control, but they are not long-term maintenance treatment. Other immune-targeting medicines may be needed to obtain lasting control without repeated steroids.

The choice depends on severity, previous response, other health conditions and your preferences. Follow the prescribed steroid course and any reduction plan. Do not stop suddenly without advice.

How do we check whether inflammation has settled?

Symptoms and inflammation do not always match. Follow-up may include blood tests, calprotectin and selected endoscopy. These checks help distinguish ongoing inflammation from another cause of symptoms and assess treatment safety. They do not mean you need a colonoscopy at every appointment.

Longstanding colonic inflammation can increase bowel cancer risk. I tailor surveillance to how long and how widely the bowel has been affected, previous findings and other risks.

It is separate from routine population screening. A negative FIT does not replace recommended surveillance. Your endoscopy and/or histology report will record the follow-up once tissue results are available.

A focused check of lower-bowel inflammation may use flexible sigmoidoscopy. This is different from cancer surveillance. →

Daily care and what to do if symptoms worsen

Keep taking prescribed maintenance treatment even when you feel well, unless the treating team changes it. If blood, urgency or diarrhoea increase, contact the team looking after your IBD or your GP. Infection, medicine effects and inflammation can produce similar symptoms, so do not automatically restart leftover steroids or add anti-diarrhoeal medicine.

There is no single diet that cures UC. Food adjustments and dietitian support can help symptoms, nutrition and recovery without unnecessary restriction. Tell me about weight loss, difficulty eating, pregnancy plans or problems keeping up with treatment. These affect the plan and should be discussed before stopping medicines.

When surgery is considered

Surgery may be appropriate when treatment does not control the disease, when precancerous changes or cancer are found, or during a severe complication. It can substantially improve health and quality of life. A colorectal surgeon explains the options, including an ileostomy or, for selected people, an internal pouch made from small bowel.

Removing the colon and rectum removes the colitis in those organs, but it does not guarantee that every IBD-related problem disappears. A pouch can develop inflammation, and conditions outside the bowel may persist. Follow-up depends on the operation and your individual findings.

Related information

• IBD: understanding the diagnosis
• How Crohn's disease differs
• Choosing and monitoring IBD treatment
• Using calprotectin to assess inflammation
• Why biopsies are taken
• Understanding your tissue report